US20230408594A1 - Method for diagnosing battery pack - Google Patents

Method for diagnosing battery pack Download PDF

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Publication number
US20230408594A1
US20230408594A1 US18/030,650 US202118030650A US2023408594A1 US 20230408594 A1 US20230408594 A1 US 20230408594A1 US 202118030650 A US202118030650 A US 202118030650A US 2023408594 A1 US2023408594 A1 US 2023408594A1
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Prior art keywords
wire
bonded portion
battery cell
magnetic field
battery pack
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US18/030,650
Inventor
Hye Yun BAE
Kyoung Choon MIN
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LG Energy Solution Ltd
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LG Energy Solution Ltd
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Assigned to LG ENERGY SOLUTION, LTD. reassignment LG ENERGY SOLUTION, LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BAE, Hye Yun, MIN, KYOUNG CHOON
Publication of US20230408594A1 publication Critical patent/US20230408594A1/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/385—Arrangements for measuring battery or accumulator variables
    • G01R31/3865—Arrangements for measuring battery or accumulator variables related to manufacture, e.g. testing after manufacture
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/3644—Constructional arrangements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/0022—Radiation pyrometry, e.g. infrared or optical thermometry for sensing the radiation of moving bodies
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/0066—Radiation pyrometry, e.g. infrared or optical thermometry for hot spots detection
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/0096—Radiation pyrometry, e.g. infrared or optical thermometry for measuring wires, electrical contacts or electronic systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/48—Thermography; Techniques using wholly visual means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/60—Radiation pyrometry, e.g. infrared or optical thermometry using determination of colour temperature
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00—Investigating or analyzing materials by the use of thermal means
    • G01N25/72—Investigating presence of flaws
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/396—Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/10—Plotting field distribution ; Measuring field distribution
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/18—Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/18—Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast
    • H04N7/183—Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast for receiving images from a single remote source
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J2005/0077—Imaging
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/032—Measuring direction or magnitude of magnetic fields or magnetic flux using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present disclosure relates to a battery pack diagnosis method, and more particularly, to a battery pack diagnosis method capable of exactly diagnosing a bonding state between a plurality of battery cells and a plurality of wires connecting the battery cells in a battery pack.
  • a battery pack is manufactured by storing a plurality of battery cells in a housing and connecting the plurality of battery cells by using a bus bar and a wire.
  • a defect may be generated in a bonded portion of the battery cell and the wire.
  • the corresponding battery cell When the defect is generated in the bonded portion of the battery cell and the wire, the corresponding battery cell may have a great variation in internal resistance while being charged or discharged.
  • the corresponding battery cell has a voltage greater than that of a normal battery cell disposed therearound when charged and has a voltage less than that of a normal battery cell disposed therearound when discharged.
  • a bonding state of the bonded portion has to be diagnosed by performing an inspection on the bonding state of the bonded portion of the battery cell and the wire in a battery pack manufacturing process.
  • the present disclosure provides a battery pack diagnosis method capable of exactly diagnosing a bonding state between a plurality of battery cells and a plurality of wires connecting the battery cells in a battery pack.
  • a battery pack diagnosis method includes: a battery pack manufacturing process of manufacturing a battery pack by bonding-connecting a battery cell and a wire; a battery cell charging and discharging process of charging and discharging the battery cell through the wire; a battery pack thermal image photographing process of photographing a thermal image of the battery pack; a thermal image reading process of reading a bonding state of a bonded portion of the battery cell and the wire from photographed thermal image data; a battery pack magnetic field image photographing process of photographing a magnetic field image of the battery pack; a magnetic field image reading process of reading a bonding state of the bonded portion of the battery cell and the wire from photographed magnetic field image data; and a wire bonding state defect determining process of finally determining a bonding state of the battery cell and the wire by combining thermal image reading result information obtained in the thermal image reading process and magnetic field image reading result information obtained in the magnetic field image reading process.
  • the battery pack thermal image photographing process may generate a thermal image by photographing a predetermined plane on which the wire is positioned, and the photographed thermal image may have a predetermined pixel size less than at least one of a thickness of the wire and a size of a bonded portion of the wire.
  • the thermal image reading process may include: a thermal image contour generating process of extracting a predetermined contour in the photographed thermal image and generating a shape of the bonded portion of the battery cell and the wire; a bonded portion temperature reading process of reading a temperature of the bonded portion of the battery cell and the wire from photographed thermal image data as one of a high temperature and a low temperature; a bonded portion abnormal connection determining process of determining a bonding state of the bonded portion as an abnormal connection-confirmed state when the bonded portion of the battery cell and the wire has a temperature greater than a predetermined reference temperature; a bonded portion normal connection-considered determining process of determining a bonding state of the bonded portion as a normal connection-considered state when the bonded portion of the battery cell and the wire has a temperature less than the reference temperature; and a thermal image reading result information generating process of generating thermal image reading result information by matching position information of the bonded portion with the bonding state of the bonded portion.
  • the battery pack magnetic field image photographing process may generate a magnetic field image by photographing the same predetermined plane as that photographed to obtain the thermal image, and the photographed magnetic field image may have a predetermined pixel size determined in correspondence to that of the photographed thermal image.
  • the magnetic field image reading process may include: a magnetic field image contour generating process of generating a shape of the bonded portion of the battery cell and the wire in the photographed magnetic field image by using the contour extracted from the thermal image reading process; a bonded portion magnetic field intensity reading process of reading the magnetic field intensity of the bonded portion of the battery cell and the wire from photographed magnetic field image data; a bonded portion normal connection determining process of determining the bonding state of the bonded portion as a normal connection-confirmed state when the bonded portion of the battery cell and the wire has a magnetic field intensity greater than a predetermined reference intensity; a bonded portion abnormal connection-considered determining process of determining the bonding state of the bonded portion as an abnormal connection-considered state when the bonded portion of the battery cell and the wire has a magnetic field intensity less than the reference intensity; and a magnetic field image reading result information generating process of generating magnetic field image reading result information by matching position information of the bonded portion with the bonding state of the bonded portion.
  • the wire bonding state defect determining process may finally determine the bonding state of the bonded portion of the battery cell and the wire as one state selected from a normal connection state, an abnormal connection state, and an abnormal broken state by comparing the thermal image reading result information with the magnetic field image reading result information.
  • the wire bonding state defect determining process may finally determine: the bonding state of the bonded portion as the abnormal connection state when the bonding state of the bonded portion of the battery cell and the wire is an abnormal connection-confirmed state; the bonding state of the bonded portion as the normal connection state when the bonding state of the bonded portion of the battery cell and the wire is a normal connection-confirmed state; and the bonding state of the bonded portion as the abnormal broken state when the bonding state of the bonded portion of the battery cell and the wire is a normal connection-considered state or an abnormal connection-considered state.
  • the battery pack thermal image photographing process and the battery pack magnetic field image photographing process may be simultaneously performed.
  • the battery pack thermal image photographing process and the battery pack magnetic field image photographing process may be performed in a predetermined order with a predetermined time difference.
  • the bonding state between the battery cell and the wire connected thereto in the battery pack may be exactly diagnosed by combining the thermal image reading result of the battery pack with the magnetic field image reading result of the battery pack.
  • the wire having the defective bonding state may not be left out from the diagnosis result. That is, the bonding state may be exactly diagnosed in comparison with the case of reading only the thermal image or the case of reading only the magnetic field image.
  • FIG. 1 is a flowchart representing a battery pack diagnosis method in accordance with an exemplary embodiment.
  • FIGS. 2 and 3 are schematic views exemplarily illustrating a battery pack manufacturing process in accordance with an exemplary embodiment.
  • FIG. 4 is a schematic view exemplarily illustrating a battery cell charging and discharging process in accordance with an exemplary embodiment.
  • FIG. 5 is a schematic view exemplarily illustrating a battery pack thermal image photographing process in accordance with an exemplary embodiment.
  • FIG. 6 is a conceptual view for explaining a thermal image reading process in accordance with an exemplary embodiment.
  • FIG. 7 is a schematic view exemplarily illustrating a battery pack magnetic field image photographing process in accordance with an exemplary embodiment.
  • FIG. 8 is a conceptual view for explaining a magnetic field image reading process in accordance with an exemplary embodiment.
  • FIG. 1 is a flowchart representing a battery pack diagnosis method in accordance with an exemplary embodiment.
  • the battery pack diagnosis method in accordance with an exemplary embodiment includes a battery pack manufacturing process S 100 , a battery cell charging and discharging process S 200 , a battery pack thermal image photographing process S 300 , a thermal image reading process S 400 , a battery pack magnetic field image photographing process S 500 , a magnetic field image reading process S 600 , and a wire bonding state defect determining process S 700 .
  • FIGS. 2 and 3 are schematic views exemplarily illustrating a battery pack manufacturing process in accordance with an exemplary embodiment.
  • the process of manufacturing the battery pack manufactures a battery pack B by connecting a battery cell 30 and a wire W through bonding.
  • the process of manufacturing the battery pack may include a battery cell storing process S 110 and a wire bonding process S 120 .
  • a battery pack housing 10 a battery cell holder 20 , a plurality of battery cells 30 , and a bus bar 40 are prepared. Thereafter, the battery cell holder 20 may be stored in the battery pack housing 10 , and the plurality of battery cells 30 may be stored in the battery cell holder 20 . Also, the bus bar 40 may be seated on the plurality of battery cells 30 .
  • the battery pack housing 10 may have a rectangular container shape of which the inside is opened upward.
  • the battery pack housing 10 may have various shapes.
  • the battery cell holder 20 may be made of various materials and various shapes capable of fixing the plurality of battery cells 30 .
  • the battery cell 30 may be a cylindrical secondary battery cell extending in a vertical direction.
  • the battery cell 30 may be a can-type secondary battery cell extending in a vertical direction.
  • the battery cells 30 may be arranged in a horizontal direction to form a predetermined arrangement.
  • a wire bonding process may manufacture a battery pack B such that a plurality of wires W are respectively arranged in a plurality of through-holes H defined in the bus bar 40 to connect the plurality of battery cells 30 and the bus bar 40 , and then, by performing a wire bonding, one end of each of the plurality of wires W is connected to each of the plurality of battery cells 30 , and the other end of each of the plurality of wires W is connected to the bus bar 40 .
  • the one end of the wire W may not normally contact the battery cell 30 .
  • the bonded portion may have an abnormally small area. Also, the bonded portion may be completely broken.
  • a bonded portion of the bus bar 40 and the other end of the wire W may be damaged, and the bonded portion may be completely broken. Even in this case, a bonding state of the bonded portion may be determined by the same method through processes below.
  • FIG. 4 is a schematic view exemplarily illustrating the battery cell charging and discharging process in accordance with an exemplary embodiment.
  • the battery cell charging and discharging process charges and discharges the battery cell through the wire.
  • the battery cell charging and discharging process may include a process of seating the manufactured battery pack B on a support part 50 , a process of connecting a charge and discharge unit 60 to an input and output terminal (not shown) of the battery pack B, which is connected with the battery cell 30 through the wire W, and a process of charging or discharging the battery cell 30 in the battery pack B by using the charge and discharge unit 60 .
  • the charge and discharge unit 60 may include a predetermined charge source (not shown) and a predetermined discharge rod (not shown). While the battery cell 30 is charged or discharged by using the charge and discharge unit 60 , a current flow passing the input and output terminal, the wire W, and the battery cell 30 is formed. Here, when the bonded portion of the battery cell 30 and the wire W is damaged, an abnormal current flow may be formed, or a current flow may not be formed.
  • the bonded portion when the bonded portion has an abnormally small area as the bonded portion of the battery cell 30 and the wire W is damaged, resistance of the bonded portion may increase, and an abnormal current flow may be formed.
  • the bonded portion may have a temperature greater than that of a surrounding portion thereof while a current flows through the bonded portion.
  • the bonded portion of the battery cell 30 and the wire W When the bonded portion of the battery cell 30 and the wire W is not damaged, or when the bonded portion of the battery cell 30 and the wire W is completely broken, the bonded portion may have a temperature less than that of the damaged bonded portion.
  • a current intensity of the bonded portion may be less than a surrounding portion thereof or have a value of 0, and a magnetic field intensity of the bonded portion may be less than that of a surrounding portion thereof.
  • a current intensity of the bonded portion may be greater than that of the above case, and thus a magnetic field intensity may be also greater than that of the above case.
  • FIG. 5 is a schematic view exemplarily illustrating the battery pack thermal image photographing process in accordance with an exemplary embodiment.
  • the battery pack thermal image photographing process photographs a thermal image of the battery pack B.
  • the battery pack thermal image photographing process may include a process of seating the battery pack B on the support part 50 and arranging a thermal image photographing unit 70 above the support part 50 and a process of photographing a thermal image of a predetermined plane on which the wire W is disposed, e.g., a top surface of the battery pack B, by using the thermal image photographing unit 70 .
  • the battery pack B may be seated on the support part 50 having a top surface capable of supporting the battery pack B, and then the thermal image photographing unit 70 connected with a diagnosis part 80 may be moved above the battery pack B. Also, an infrared ray emitted from the top surface of the battery pack B may be detected by using a plurality of detection elements (not shown) forming a predetermined focal plane arrangement of a focal plane of the thermal image photographing unit 70 , and a thermal image of the top surface of the battery pack B may be photographed.
  • the photographed thermal image may have a predetermined pixel size that is determined in correspondence to a size of the wire W.
  • the photographed thermal image may have a predetermined pixel size less than at least one of a thickness of the wire W and a size of a bonded portion of the wire W to distinguish the wire W in the photographed thermal image.
  • the photographed thermal image may have a predetermined pixel size less than a diameter of the battery cell 30 .
  • FIG. 6 is a conceptual view for explaining the thermal image reading process in accordance with an exemplary embodiment.
  • the thermal image reading process reads a bonding state of the bonded portion of the battery cell 30 and the wire W from photographed thermal image data DB 1 . This process may be performed in the diagnosis part 80 .
  • the thermal image reading process may include: a thermal image contour generating process of extracting a predetermined contour in the photographed thermal image and generating a shape of the bonded portion of the battery cell 30 and the wire W; a bonded portion temperature reading process of reading a temperature of the bonded portion of the battery cell 30 and the wire W from the photographed thermal image data DB 1 as one of a high temperature and a low temperature; a bonded portion abnormal connection determining process of determining a bonding state of the bonded portion as an abnormal connection-confirmed state when the bonded portion of the battery cell and the wire has a high temperature; a bonded portion normal connection-considered determining process of determining a bonding state of the bonded portion as a normal connection-considered state when the bonded portion of the battery cell and the wire has a low temperature; and a thermal image reading result information generating process of generating the thermal image reading result information by matching position information of the bonded portion with the bonding state of the bonded portion.
  • a predetermined contour is extracted from the photographed thermal image.
  • predetermined heat is generated from each of the battery cell 30 , the bus bar 40 , and the wire W and transferred to a surrounding area while the battery cell 30 is charged and discharged.
  • each of the battery cell 30 , the bus bar 40 , and the wire W may have a different predetermined size, material, and property, and when thermal images of the battery cell 30 , the bus bar 40 , and the wire W are reviewed by photographing the same, a minute temperature difference may be generated at a boundary therebetween, and a contour caused by the temperature difference may be generated.
  • a shape of the bonded portion of the battery cell 30 and the wire W may be generated by extracting a predetermined contour from the photographed thermal image, and through this, pixels corresponding to the bonded portion of the wire W may be distinguished from pixels that are not.
  • the bonded portion of the wire W in the photographed thermal image may be known.
  • pixels of a photographed thermal image P 1 are divided based on temperatures. That is, the pixels of the photographed thermal image P 1 is divided into a pixel A 1 and A 2 having a high temperature T 2 greater than a predetermined reference temperature and a pixel having a low temperature T 1 less than the reference temperature.
  • Each of the high temperature T 2 and the low temperature T 1 may have a predetermined temperature range.
  • the low temperature T 1 less than the reference temperature may have a predetermined temperature range
  • the high temperature T 2 may have a predetermined temperature range greater than that of the low temperature T 1 .
  • the reference temperature may be within a range of a surface temperature of the wire W when the battery cell 30 is charged or discharged in a state in which the bus bar 40 , the wire W, and the battery cell 30 are normally wire-bonded and connected.
  • the surface temperature may be obtained by a theoretical calculation or a predetermined experiment of repeatedly measuring a temperature of the wire W connected with the battery cell 30 while the battery cell 30 is charged or discharged under the room temperature or the standard temperature.
  • the pixel A 1 and A 2 having the high temperature T 2 is distinguished from the pixel having the low temperature, and a closed curve (not shown) is formed to surround the pixel A 1 and A 2 having the high temperature T 2 .
  • a closed curve (not shown) is formed to surround the pixel A 1 and A 2 having the high temperature T 2 .
  • whether the wire W is positioned inside the closed curve is checked. That is, whether the contour extracted from the thermal image P 1 to distinguish the pixels corresponding to the bonded portion of the wire W from the pixels that are not overlaps the closed curve surrounding the pixels A 1 and A 2 having the high temperature T 2 may be checked, and then, when the contour overlaps the closed curve, whether the wire W is positioned inside the closed curve may be checked.
  • position information of the bonded portion of the wire W positioned inside the closed curve is obtained.
  • the position information of the bonded portion of the wire W positioned inside the closed curve may be obtained in the form of a predetermined coordinate by using an installation height, an installation angle, a view angle, and a resolution X-Y of the thermal image photographing unit 70 and a height and an area of the top surface of the battery pack B.
  • position information of the bonded portion of the wire W positioned outside the closed curve may be obtained.
  • the bonded portion of the wire W positioned inside the closed curve is determined as the abnormal connection-confirmed state. Also, the bonded portion of the wire W positioned outside the closed curve is determined as the normal connection-considered state.
  • FIG. 7 is a schematic view exemplarily illustrating the battery pack magnetic field image photographing process in accordance with an exemplary embodiment.
  • the battery pack magnetic field image photographing process photographs a magnetic field image of the battery pack B.
  • a magnetized state of the target When a current and a magnetic field are simultaneously applied to a target, a magnetized state of the target may form a specific angle, and through this angle, a size of the magnetic field generating a current may be measured. Also, reflected light generated as a laser beam is incident to the target may be collected to detect an intensity thereof, and an intensity of the magnetic field may be calculated based on the detected intensity of the reflected light. Besides, the intensity of the magnetic field may be obtained by using all sorts of magnetic sensors, and from this, a magnetic field image may be generated.
  • the magnetic field image of the battery pack B may be photographed by using a magnetic field image photographing unit 80 including a predetermined magnetic sensor arrangement.
  • the battery pack magnetic field image photographing process may include a process of positioning the magnetic field image photographing unit 80 above the support part 50 and a process of photographing a magnetic field image of a predetermined plane on which the wire W is positioned by using the magnetic field image photographing unit 80 .
  • the magnetic field image photographing unit 80 may be positioned on the top surface of the battery pack B, and then a magnetic field image of the top surface of the battery pack B may be photographed while scanning the top surface of the battery pack B in a horizontal direction. That is, the magnetic field image is generated by photographing the same predetermined plane as that photographed to obtain the thermal image.
  • the photographed magnetic field image may have a predetermined pixel size that is determined in correspondence to the pixel size of the photographed thermal image.
  • the magnetic field image may have the same pixel size as that of the thermal image.
  • the battery pack thermal image photographing process and the battery pack magnetic field image photographing process may be performed while the battery cell charging and discharging process is performed, and here, the two processes may be simultaneously performed.
  • the thermal image and the magnetic field image may have the same photographed area and the same photographed time.
  • the battery pack thermal image photographing process and the battery pack magnetic field image photographing process may be performed in a predetermined order with a predetermined time difference.
  • FIG. 8 is a conceptual view for explaining the magnetic field image reading process in accordance with an exemplary embodiment.
  • the magnetic field image reading process may read the bonding state of the bonded portion of the battery cell and the wire from photographed magnetic field image data DB 2 and be performed by the diagnosis part 80 .
  • the magnetic field image reading process may include: a magnetic field image contour generating process of generating a shape of the bonded portion of the battery cell 30 and the wire W in the photographed magnetic field image by using the contour extracted from the thermal image reading process; a bonded portion magnetic field intensity reading process of reading the magnetic field intensity of the bonded portion of the battery cell and the wire from the photographed magnetic field image data DB 2 ; a bonded portion normal connection determining process of determining the bonding state of the bonded portion as a normal connection-confirmed state when the bonded portion of the battery cell and the wire has a magnetic field intensity greater than a predetermined reference intensity; a bonded portion abnormal connection-considered determining process of determining the bonding state of the bonded portion as an abnormal connection-considered state when the bonded portion of the battery cell and the wire has a magnetic field intensity less than the reference intensity; and a magnetic field image reading result information generating process of generating the magnetic field image reading result information by matching position information of the bonded portion with the bonding state of the
  • pixels of a magnetic field image P 2 photographed with a predetermined resolution X-Y may be distinguished by different colors or brightness according to magnetic field intensities, and distinguished into a pixel having a magnetic field intensity corresponding to an intensity m 2 in a predetermined range greater than the reference intensity and a pixel having a magnetic field intensity corresponding to an intensity m 1 in a predetermined range less than the reference intensity.
  • a shape of the bonded portion of the battery cell 30 and the wire W is generated in the photographed magnetic field image P 2 , a closed curve (not shown) surrounding the pixels having a magnetic field intensity greater than the reference intensity is generated, whether the bonded portion of the wire W is positioned inside the closed curve is checked, and position information of the wire W inside the closed curve and position information of the wire W outside the closed curve are obtained.
  • the magnetic field intensity has a unit of micro-Tesla ( ⁇ Tesla).
  • the reference intensity may be within a range of a magnetic field intensity measured from the wire W while the battery cell 30 is charged or discharged in a state in which the bus bar 40 , the wire W, and the battery cell 30 are normally wire-bonded and connected.
  • the reference intensity may be obtained by a theoretical calculation or a predetermined experiment of repeatedly measuring a magnetic field intensity generated from the wire W connected with the battery cell 30 while the battery cell 30 is charged or discharged under the room temperature or the standard temperature.
  • the bonded portion of the wire W positioned inside the closed curve is determined as the normal connection-confirmed state, and the rest is determined as the abnormal connection-considered state.
  • the wire bonding state defect determining process is performed in the diagnosis part 80 and finally determines the bonding state of the bonded portion of the battery cell and the wire by combining the thermal image reading result information obtained in the thermal image reading process and the magnetic field image reading result information obtained in the magnetic field image reading process.
  • the wire bonding state defect determining process may finally determine the bonding state of the bonded portion of the battery cell and the wire as one state selected from the normal connection state, the abnormal connection state, and the abnormal broken state by comparing the thermal image reading result information with the magnetic field image reading result information.
  • the bonding state of the bonded portion of the battery cell and the wire is the abnormal connection-confirmed state by comparing the thermal image reading result information with the magnetic field image reading result information, the bonding state of the bonded portion may be finally determined as the abnormal connection state.
  • the feature in which the bonding state of the bonded portion of the battery cell and the wire is the abnormal connection-confirmed state represents that the bonded portion has a high temperature. That is, when the bonded portion has the high temperature, the bonding state of the bonded portion is finally determined as the abnormal connection state regardless of the magnetic field image reading result.
  • the bonding state of the bonded portion of the battery cell and the wire is the normal connection-confirmed state by comparing the thermal image reading result information with the magnetic field image reading result information, the bonding state of the bonded portion may be finally determined as the normal connection state.
  • the feature in which the bonding state of the bonded portion of the battery cell and the wire is the normal connection-confirmed state represents that the bonded portion has a strong magnetic field intensity.
  • the bonding state of the bonded portion is finally determined as the normal connection state regardless of the thermal image reading result.
  • the bonding state of the bonded portion of the battery cell and the wire is the normal connection-considered state or the abnormal connection-considered state by comparing the thermal image reading result information with the magnetic field image reading result information, the bonding state of the bonded portion may be finally determined as the abnormal broken state.
  • the bonding state may not be confirmed by only the temperature difference or only the magnetic field image.
  • a completely broken bonded portion and a normally connected bonded portion may not generate heat or may generate a small amount of heat, and since temperatures thereof may be greatly affected, the two portions may not be distinguished in terms of the temperature.
  • each of a damaged bonded portion and a completely broken bonded portion has a small magnetic field intensity, the two portions may not be distinguished in terms of the magnetic field intensity.
  • the bonding state of the bonded portion may be exactly finally determined as the abnormal broken state by comparing the thermal image reading result information with the magnetic field image reading result information to check the bonding state of the bonded portion of the battery cell and the wire is included in all of the normal connection-considered state and the abnormal state-considered state, i.e., by cross-validating the bonding state in terms of the thermal state and the magnetic field intensity.

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Abstract

Discussed is a battery pack diagnosis method including a battery pack manufacturing process, a battery cell charging and discharging process, a battery pack thermal image photographing process, a thermal image reading process, a battery pack magnetic field image photographing process, a magnetic field image reading process, and a wire bonding state defect determining process of finally determining a bonding state of a battery cell and a wire by combining thermal image reading result information obtained in the thermal image reading process and magnetic field image reading result information obtained in the magnetic field image reading process in order to exactly diagnose the bonding state of the battery cell and the wire connecting the battery cell in the battery pack.

Description

    TECHNICAL FIELD
  • The present disclosure relates to a battery pack diagnosis method, and more particularly, to a battery pack diagnosis method capable of exactly diagnosing a bonding state between a plurality of battery cells and a plurality of wires connecting the battery cells in a battery pack.
    • BACKGROUND ART
  • A battery pack is manufactured by storing a plurality of battery cells in a housing and connecting the plurality of battery cells by using a bus bar and a wire. In the battery pack, a defect may be generated in a bonded portion of the battery cell and the wire.
  • When the defect is generated in the bonded portion of the battery cell and the wire, the corresponding battery cell may have a great variation in internal resistance while being charged or discharged. For example, the corresponding battery cell has a voltage greater than that of a normal battery cell disposed therearound when charged and has a voltage less than that of a normal battery cell disposed therearound when discharged.
  • Also, when the corresponding battery cell is continuously charged or discharged, a total output of the battery pack may decrease, and short-circuit may occur in the corresponding battery cell to be ignited. Thus, a bonding state of the bonded portion has to be diagnosed by performing an inspection on the bonding state of the bonded portion of the battery cell and the wire in a battery pack manufacturing process.
  • However, in one battery pack, several hundreds of battery cells and several hundreds of wires for connecting the battery cells are stored. Thus, the bonding state of the bonded portion of each of the several hundreds of battery cells and wires may not be exactly inspected.
  • The background technology of the present invention is disclosed in patent documents below.
    • (Patent document 1) KR10-2019-0011096 A
    • (Patent document 2) KR10-2020-0056715 A
    SUMMARY
  • The present disclosure provides a battery pack diagnosis method capable of exactly diagnosing a bonding state between a plurality of battery cells and a plurality of wires connecting the battery cells in a battery pack.
  • In accordance with an exemplary embodiment, a battery pack diagnosis method includes: a battery pack manufacturing process of manufacturing a battery pack by bonding-connecting a battery cell and a wire; a battery cell charging and discharging process of charging and discharging the battery cell through the wire; a battery pack thermal image photographing process of photographing a thermal image of the battery pack; a thermal image reading process of reading a bonding state of a bonded portion of the battery cell and the wire from photographed thermal image data; a battery pack magnetic field image photographing process of photographing a magnetic field image of the battery pack; a magnetic field image reading process of reading a bonding state of the bonded portion of the battery cell and the wire from photographed magnetic field image data; and a wire bonding state defect determining process of finally determining a bonding state of the battery cell and the wire by combining thermal image reading result information obtained in the thermal image reading process and magnetic field image reading result information obtained in the magnetic field image reading process.
  • The battery pack thermal image photographing process may generate a thermal image by photographing a predetermined plane on which the wire is positioned, and the photographed thermal image may have a predetermined pixel size less than at least one of a thickness of the wire and a size of a bonded portion of the wire.
  • The thermal image reading process may include: a thermal image contour generating process of extracting a predetermined contour in the photographed thermal image and generating a shape of the bonded portion of the battery cell and the wire; a bonded portion temperature reading process of reading a temperature of the bonded portion of the battery cell and the wire from photographed thermal image data as one of a high temperature and a low temperature; a bonded portion abnormal connection determining process of determining a bonding state of the bonded portion as an abnormal connection-confirmed state when the bonded portion of the battery cell and the wire has a temperature greater than a predetermined reference temperature; a bonded portion normal connection-considered determining process of determining a bonding state of the bonded portion as a normal connection-considered state when the bonded portion of the battery cell and the wire has a temperature less than the reference temperature; and a thermal image reading result information generating process of generating thermal image reading result information by matching position information of the bonded portion with the bonding state of the bonded portion.
  • The battery pack magnetic field image photographing process may generate a magnetic field image by photographing the same predetermined plane as that photographed to obtain the thermal image, and the photographed magnetic field image may have a predetermined pixel size determined in correspondence to that of the photographed thermal image.
  • The magnetic field image reading process may include: a magnetic field image contour generating process of generating a shape of the bonded portion of the battery cell and the wire in the photographed magnetic field image by using the contour extracted from the thermal image reading process; a bonded portion magnetic field intensity reading process of reading the magnetic field intensity of the bonded portion of the battery cell and the wire from photographed magnetic field image data; a bonded portion normal connection determining process of determining the bonding state of the bonded portion as a normal connection-confirmed state when the bonded portion of the battery cell and the wire has a magnetic field intensity greater than a predetermined reference intensity; a bonded portion abnormal connection-considered determining process of determining the bonding state of the bonded portion as an abnormal connection-considered state when the bonded portion of the battery cell and the wire has a magnetic field intensity less than the reference intensity; and a magnetic field image reading result information generating process of generating magnetic field image reading result information by matching position information of the bonded portion with the bonding state of the bonded portion.
  • The wire bonding state defect determining process may finally determine the bonding state of the bonded portion of the battery cell and the wire as one state selected from a normal connection state, an abnormal connection state, and an abnormal broken state by comparing the thermal image reading result information with the magnetic field image reading result information.
  • The wire bonding state defect determining process, by comparing the thermal image reading result information with the magnetic image reading result information, may finally determine: the bonding state of the bonded portion as the abnormal connection state when the bonding state of the bonded portion of the battery cell and the wire is an abnormal connection-confirmed state; the bonding state of the bonded portion as the normal connection state when the bonding state of the bonded portion of the battery cell and the wire is a normal connection-confirmed state; and the bonding state of the bonded portion as the abnormal broken state when the bonding state of the bonded portion of the battery cell and the wire is a normal connection-considered state or an abnormal connection-considered state.
  • While the battery cell charging and discharging process is performed, the battery pack thermal image photographing process and the battery pack magnetic field image photographing process may be simultaneously performed.
  • While the battery cell charging and discharging process is performed, the battery pack thermal image photographing process and the battery pack magnetic field image photographing process may be performed in a predetermined order with a predetermined time difference.
  • In accordance with the exemplary embodiment, the bonding state between the battery cell and the wire connected thereto in the battery pack may be exactly diagnosed by combining the thermal image reading result of the battery pack with the magnetic field image reading result of the battery pack. Thus, the wire having the defective bonding state may not be left out from the diagnosis result. That is, the bonding state may be exactly diagnosed in comparison with the case of reading only the thermal image or the case of reading only the magnetic field image.
    • BRIEF DESCRIPTION OF THE DRAWINGS
  • FIG. 1 is a flowchart representing a battery pack diagnosis method in accordance with an exemplary embodiment.
  • FIGS. 2 and 3 are schematic views exemplarily illustrating a battery pack manufacturing process in accordance with an exemplary embodiment.
  • FIG. 4 is a schematic view exemplarily illustrating a battery cell charging and discharging process in accordance with an exemplary embodiment.
  • FIG. 5 is a schematic view exemplarily illustrating a battery pack thermal image photographing process in accordance with an exemplary embodiment.
  • FIG. 6 is a conceptual view for explaining a thermal image reading process in accordance with an exemplary embodiment.
  • FIG. 7 is a schematic view exemplarily illustrating a battery pack magnetic field image photographing process in accordance with an exemplary embodiment.
  • FIG. 8 is a conceptual view for explaining a magnetic field image reading process in accordance with an exemplary embodiment.
    •  DETAILED DESCRIPTION OF EMBODIMENTS
  • Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. In the figures, the dimensions of layers and regions are exaggerated for clarity of illustration. Like reference numerals refer to like elements throughout.
  • Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings.
  • 1. Battery Pack Diagnosis Method in Accordance with an Exemplary Embodiment
  • FIG. 1 is a flowchart representing a battery pack diagnosis method in accordance with an exemplary embodiment.
  • As illustrated in FIG. 1 , the battery pack diagnosis method in accordance with an exemplary embodiment includes a battery pack manufacturing process S100, a battery cell charging and discharging process S200, a battery pack thermal image photographing process S300, a thermal image reading process S400, a battery pack magnetic field image photographing process S500, a magnetic field image reading process S600, and a wire bonding state defect determining process S700.
  • 1.1. Battery Pack Manufacturing Process S100
  • FIGS. 2 and 3 are schematic views exemplarily illustrating a battery pack manufacturing process in accordance with an exemplary embodiment.
  • The process of manufacturing the battery pack manufactures a battery pack B by connecting a battery cell 30 and a wire W through bonding. The process of manufacturing the battery pack may include a battery cell storing process S110 and a wire bonding process S120.
  • 1.1.1. Battery Cell Storing Process S110
  • Referring to FIG. 2 , in the battery cell storing process, a battery pack housing 10, a battery cell holder 20, a plurality of battery cells 30, and a bus bar 40 are prepared. Thereafter, the battery cell holder 20 may be stored in the battery pack housing 10, and the plurality of battery cells 30 may be stored in the battery cell holder 20. Also, the bus bar 40 may be seated on the plurality of battery cells 30.
  • Here, the battery pack housing 10 may have a rectangular container shape of which the inside is opened upward. Alternatively, the battery pack housing 10 may have various shapes. The battery cell holder 20 may be made of various materials and various shapes capable of fixing the plurality of battery cells 30. The battery cell 30 may be a cylindrical secondary battery cell extending in a vertical direction. Alternatively, the battery cell 30 may be a can-type secondary battery cell extending in a vertical direction. The battery cells 30 may be arranged in a horizontal direction to form a predetermined arrangement.
  • 1.1.2. Wire Bonding Process S120
  • Referring to FIG. 3 , a wire bonding process may manufacture a battery pack B such that a plurality of wires W are respectively arranged in a plurality of through-holes H defined in the bus bar 40 to connect the plurality of battery cells 30 and the bus bar 40, and then, by performing a wire bonding, one end of each of the plurality of wires W is connected to each of the plurality of battery cells 30, and the other end of each of the plurality of wires W is connected to the bus bar 40.
  • Here, as a bonded portion of the battery cell 30 and the wire W is damaged, the one end of the wire W may not normally contact the battery cell 30. Thus, the bonded portion may have an abnormally small area. Also, the bonded portion may be completely broken.
  • Alternatively, a bonded portion of the bus bar 40 and the other end of the wire W may be damaged, and the bonded portion may be completely broken. Even in this case, a bonding state of the bonded portion may be determined by the same method through processes below.
  • 1.2. Battery Cell Charging and Discharging Process S200
  • FIG. 4 is a schematic view exemplarily illustrating the battery cell charging and discharging process in accordance with an exemplary embodiment.
  • Referring to FIG. 4 , the battery cell charging and discharging process charges and discharges the battery cell through the wire. The battery cell charging and discharging process may include a process of seating the manufactured battery pack B on a support part 50, a process of connecting a charge and discharge unit 60 to an input and output terminal (not shown) of the battery pack B, which is connected with the battery cell 30 through the wire W, and a process of charging or discharging the battery cell 30 in the battery pack B by using the charge and discharge unit 60.
  • Here, the charge and discharge unit 60 may include a predetermined charge source (not shown) and a predetermined discharge rod (not shown). While the battery cell 30 is charged or discharged by using the charge and discharge unit 60, a current flow passing the input and output terminal, the wire W, and the battery cell 30 is formed. Here, when the bonded portion of the battery cell 30 and the wire W is damaged, an abnormal current flow may be formed, or a current flow may not be formed.
  • For example, when the bonded portion has an abnormally small area as the bonded portion of the battery cell 30 and the wire W is damaged, resistance of the bonded portion may increase, and an abnormal current flow may be formed. In this case, the bonded portion may have a temperature greater than that of a surrounding portion thereof while a current flows through the bonded portion.
  • Also, when the bonded portion of the battery cell 30 and the wire W is completely broken, a current flow may not be formed.
  • When the bonded portion of the battery cell 30 and the wire W is not damaged, or when the bonded portion of the battery cell 30 and the wire W is completely broken, the bonded portion may have a temperature less than that of the damaged bonded portion.
  • Also, when the bonded portion of the battery cell 30 and the wire W is damaged or completely broken, a current intensity of the bonded portion may be less than a surrounding portion thereof or have a value of 0, and a magnetic field intensity of the bonded portion may be less than that of a surrounding portion thereof.
  • When the bonded portion of the battery cell 30 and the wire W is not damaged, while a current flows through the bonded portion, a current intensity of the bonded portion may be greater than that of the above case, and thus a magnetic field intensity may be also greater than that of the above case.
  • 1.3. Battery Pack Thermal Image Photographing Process S300
  • FIG. 5 is a schematic view exemplarily illustrating the battery pack thermal image photographing process in accordance with an exemplary embodiment.
  • The battery pack thermal image photographing process photographs a thermal image of the battery pack B. The battery pack thermal image photographing process may include a process of seating the battery pack B on the support part 50 and arranging a thermal image photographing unit 70 above the support part 50 and a process of photographing a thermal image of a predetermined plane on which the wire W is disposed, e.g., a top surface of the battery pack B, by using the thermal image photographing unit 70.
  • For example, the battery pack B may be seated on the support part 50 having a top surface capable of supporting the battery pack B, and then the thermal image photographing unit 70 connected with a diagnosis part 80 may be moved above the battery pack B. Also, an infrared ray emitted from the top surface of the battery pack B may be detected by using a plurality of detection elements (not shown) forming a predetermined focal plane arrangement of a focal plane of the thermal image photographing unit 70, and a thermal image of the top surface of the battery pack B may be photographed.
  • Here, the photographed thermal image may have a predetermined pixel size that is determined in correspondence to a size of the wire W. For example, the photographed thermal image may have a predetermined pixel size less than at least one of a thickness of the wire W and a size of a bonded portion of the wire W to distinguish the wire W in the photographed thermal image.
  • Alternatively, the photographed thermal image may have a predetermined pixel size less than a diameter of the battery cell 30.
  • 1.4. Thermal Image Reading Process S400
  • FIG. 6 is a conceptual view for explaining the thermal image reading process in accordance with an exemplary embodiment.
  • The thermal image reading process reads a bonding state of the bonded portion of the battery cell 30 and the wire W from photographed thermal image data DB1. This process may be performed in the diagnosis part 80.
  • Here, the thermal image reading process may include: a thermal image contour generating process of extracting a predetermined contour in the photographed thermal image and generating a shape of the bonded portion of the battery cell 30 and the wire W; a bonded portion temperature reading process of reading a temperature of the bonded portion of the battery cell 30 and the wire W from the photographed thermal image data DB1 as one of a high temperature and a low temperature; a bonded portion abnormal connection determining process of determining a bonding state of the bonded portion as an abnormal connection-confirmed state when the bonded portion of the battery cell and the wire has a high temperature; a bonded portion normal connection-considered determining process of determining a bonding state of the bonded portion as a normal connection-considered state when the bonded portion of the battery cell and the wire has a low temperature; and a thermal image reading result information generating process of generating the thermal image reading result information by matching position information of the bonded portion with the bonding state of the bonded portion.
  • More specifically, a predetermined contour is extracted from the photographed thermal image. For example, predetermined heat is generated from each of the battery cell 30, the bus bar 40, and the wire W and transferred to a surrounding area while the battery cell 30 is charged and discharged. Here, each of the battery cell 30, the bus bar 40, and the wire W may have a different predetermined size, material, and property, and when thermal images of the battery cell 30, the bus bar 40, and the wire W are reviewed by photographing the same, a minute temperature difference may be generated at a boundary therebetween, and a contour caused by the temperature difference may be generated.
  • Thus, a shape of the bonded portion of the battery cell 30 and the wire W may be generated by extracting a predetermined contour from the photographed thermal image, and through this, pixels corresponding to the bonded portion of the wire W may be distinguished from pixels that are not. Thus, the bonded portion of the wire W in the photographed thermal image may be known.
  • Thereafter, pixels of a photographed thermal image P1 are divided based on temperatures. That is, the pixels of the photographed thermal image P1 is divided into a pixel A1 and A2 having a high temperature T2 greater than a predetermined reference temperature and a pixel having a low temperature T1 less than the reference temperature. Each of the high temperature T2 and the low temperature T1 may have a predetermined temperature range. For example, the low temperature T1 less than the reference temperature may have a predetermined temperature range, and the high temperature T2 may have a predetermined temperature range greater than that of the low temperature T1.
  • For example, the reference temperature may be within a range of a surface temperature of the wire W when the battery cell 30 is charged or discharged in a state in which the bus bar 40, the wire W, and the battery cell 30 are normally wire-bonded and connected. Here, the surface temperature may be obtained by a theoretical calculation or a predetermined experiment of repeatedly measuring a temperature of the wire W connected with the battery cell 30 while the battery cell 30 is charged or discharged under the room temperature or the standard temperature.
  • Thereafter, the pixel A1 and A2 having the high temperature T2 is distinguished from the pixel having the low temperature, and a closed curve (not shown) is formed to surround the pixel A1 and A2 having the high temperature T2. Thereafter, whether the wire W is positioned inside the closed curve is checked. That is, whether the contour extracted from the thermal image P1 to distinguish the pixels corresponding to the bonded portion of the wire W from the pixels that are not overlaps the closed curve surrounding the pixels A1 and A2 having the high temperature T2 may be checked, and then, when the contour overlaps the closed curve, whether the wire W is positioned inside the closed curve may be checked.
  • Thereafter, position information of the bonded portion of the wire W positioned inside the closed curve is obtained. For example, the position information of the bonded portion of the wire W positioned inside the closed curve may be obtained in the form of a predetermined coordinate by using an installation height, an installation angle, a view angle, and a resolution X-Y of the thermal image photographing unit 70 and a height and an area of the top surface of the battery pack B. In the same manner, position information of the bonded portion of the wire W positioned outside the closed curve may be obtained.
  • Thereafter, the bonded portion of the wire W positioned inside the closed curve is determined as the abnormal connection-confirmed state. Also, the bonded portion of the wire W positioned outside the closed curve is determined as the normal connection-considered state.
  • 1.5. Battery Pack Magnetic Field Image Photographing Process S500
  • FIG. 7 is a schematic view exemplarily illustrating the battery pack magnetic field image photographing process in accordance with an exemplary embodiment.
  • Referring to FIG. 7 , the battery pack magnetic field image photographing process photographs a magnetic field image of the battery pack B.
  • When a current and a magnetic field are simultaneously applied to a target, a magnetized state of the target may form a specific angle, and through this angle, a size of the magnetic field generating a current may be measured. Also, reflected light generated as a laser beam is incident to the target may be collected to detect an intensity thereof, and an intensity of the magnetic field may be calculated based on the detected intensity of the reflected light. Besides, the intensity of the magnetic field may be obtained by using all sorts of magnetic sensors, and from this, a magnetic field image may be generated.
  • For example, the magnetic field image of the battery pack B may be photographed by using a magnetic field image photographing unit 80 including a predetermined magnetic sensor arrangement. The battery pack magnetic field image photographing process may include a process of positioning the magnetic field image photographing unit 80 above the support part 50 and a process of photographing a magnetic field image of a predetermined plane on which the wire W is positioned by using the magnetic field image photographing unit 80.
  • For example, the magnetic field image photographing unit 80 may be positioned on the top surface of the battery pack B, and then a magnetic field image of the top surface of the battery pack B may be photographed while scanning the top surface of the battery pack B in a horizontal direction. That is, the magnetic field image is generated by photographing the same predetermined plane as that photographed to obtain the thermal image. Here, the photographed magnetic field image may have a predetermined pixel size that is determined in correspondence to the pixel size of the photographed thermal image. Specifically, the magnetic field image may have the same pixel size as that of the thermal image.
  • The battery pack thermal image photographing process and the battery pack magnetic field image photographing process, which are described above, may be performed while the battery cell charging and discharging process is performed, and here, the two processes may be simultaneously performed. Thus, the thermal image and the magnetic field image may have the same photographed area and the same photographed time. Alternatively, the battery pack thermal image photographing process and the battery pack magnetic field image photographing process may be performed in a predetermined order with a predetermined time difference.
  • 1.6. Magnetic Field Image Reading Process S600
  • FIG. 8 is a conceptual view for explaining the magnetic field image reading process in accordance with an exemplary embodiment.
  • Referring to FIG. 8 , the magnetic field image reading process may read the bonding state of the bonded portion of the battery cell and the wire from photographed magnetic field image data DB2 and be performed by the diagnosis part 80.
  • The magnetic field image reading process may include: a magnetic field image contour generating process of generating a shape of the bonded portion of the battery cell 30 and the wire W in the photographed magnetic field image by using the contour extracted from the thermal image reading process; a bonded portion magnetic field intensity reading process of reading the magnetic field intensity of the bonded portion of the battery cell and the wire from the photographed magnetic field image data DB2; a bonded portion normal connection determining process of determining the bonding state of the bonded portion as a normal connection-confirmed state when the bonded portion of the battery cell and the wire has a magnetic field intensity greater than a predetermined reference intensity; a bonded portion abnormal connection-considered determining process of determining the bonding state of the bonded portion as an abnormal connection-considered state when the bonded portion of the battery cell and the wire has a magnetic field intensity less than the reference intensity; and a magnetic field image reading result information generating process of generating the magnetic field image reading result information by matching position information of the bonded portion with the bonding state of the bonded portion.
  • That is, pixels of a magnetic field image P2 photographed with a predetermined resolution X-Y may be distinguished by different colors or brightness according to magnetic field intensities, and distinguished into a pixel having a magnetic field intensity corresponding to an intensity m2 in a predetermined range greater than the reference intensity and a pixel having a magnetic field intensity corresponding to an intensity m1 in a predetermined range less than the reference intensity. Thus, by using the contour extracted from the thermal image reading process, a shape of the bonded portion of the battery cell 30 and the wire W is generated in the photographed magnetic field image P2, a closed curve (not shown) surrounding the pixels having a magnetic field intensity greater than the reference intensity is generated, whether the bonded portion of the wire W is positioned inside the closed curve is checked, and position information of the wire W inside the closed curve and position information of the wire W outside the closed curve are obtained. The magnetic field intensity has a unit of micro-Tesla (μTesla). The reference intensity may be within a range of a magnetic field intensity measured from the wire W while the battery cell 30 is charged or discharged in a state in which the bus bar 40, the wire W, and the battery cell 30 are normally wire-bonded and connected. Here, the reference intensity may be obtained by a theoretical calculation or a predetermined experiment of repeatedly measuring a magnetic field intensity generated from the wire W connected with the battery cell 30 while the battery cell 30 is charged or discharged under the room temperature or the standard temperature.
  • Thereafter, the bonded portion of the wire W positioned inside the closed curve is determined as the normal connection-confirmed state, and the rest is determined as the abnormal connection-considered state.
  • 1.7. Wire Bonding State Defect Determining Process S700
  • The wire bonding state defect determining process is performed in the diagnosis part 80 and finally determines the bonding state of the bonded portion of the battery cell and the wire by combining the thermal image reading result information obtained in the thermal image reading process and the magnetic field image reading result information obtained in the magnetic field image reading process.
  • Specifically, the wire bonding state defect determining process may finally determine the bonding state of the bonded portion of the battery cell and the wire as one state selected from the normal connection state, the abnormal connection state, and the abnormal broken state by comparing the thermal image reading result information with the magnetic field image reading result information.
  • That is, when the bonding state of the bonded portion of the battery cell and the wire is the abnormal connection-confirmed state by comparing the thermal image reading result information with the magnetic field image reading result information, the bonding state of the bonded portion may be finally determined as the abnormal connection state.
  • For example, the feature in which the bonding state of the bonded portion of the battery cell and the wire is the abnormal connection-confirmed state represents that the bonded portion has a high temperature. That is, when the bonded portion has the high temperature, the bonding state of the bonded portion is finally determined as the abnormal connection state regardless of the magnetic field image reading result.
  • Also, when the bonding state of the bonded portion of the battery cell and the wire is the normal connection-confirmed state by comparing the thermal image reading result information with the magnetic field image reading result information, the bonding state of the bonded portion may be finally determined as the normal connection state.
  • For example, the feature in which the bonding state of the bonded portion of the battery cell and the wire is the normal connection-confirmed state represents that the bonded portion has a strong magnetic field intensity. In this case, the bonding state of the bonded portion is finally determined as the normal connection state regardless of the thermal image reading result.
  • Also, when the bonding state of the bonded portion of the battery cell and the wire is the normal connection-considered state or the abnormal connection-considered state by comparing the thermal image reading result information with the magnetic field image reading result information, the bonding state of the bonded portion may be finally determined as the abnormal broken state.
  • That is, when the bonded portion of the battery cell and the wire is completely broken, the bonding state may not be confirmed by only the temperature difference or only the magnetic field image.
  • For example, a completely broken bonded portion and a normally connected bonded portion may not generate heat or may generate a small amount of heat, and since temperatures thereof may be greatly affected, the two portions may not be distinguished in terms of the temperature.
  • Also, since each of a damaged bonded portion and a completely broken bonded portion has a small magnetic field intensity, the two portions may not be distinguished in terms of the magnetic field intensity.
  • However, in accordance with an exemplary embodiment, the bonding state of the bonded portion may be exactly finally determined as the abnormal broken state by comparing the thermal image reading result information with the magnetic field image reading result information to check the bonding state of the bonded portion of the battery cell and the wire is included in all of the normal connection-considered state and the abnormal state-considered state, i.e., by cross-validating the bonding state in terms of the thermal state and the magnetic field intensity.
  • Although the embodiments of the present invention have been described, it is understood that the present invention should not be limited to these embodiments. Thus, the preferred embodiments should be considered in descriptive sense only and not for purposes of limitation, and also the technical scope of the invention is not limited to the embodiments. Therefore, it will be readily understood by those skilled in the art that various modifications and changes can be made thereto without departing from the spirit and scope of the present invention defined by the appended claims.
    • DESCRIPTION OF THE REFERENCE SIGNS
      • 10: Battery pack housing
      • 20: Battery cell holder
      • 30: Battery cell
      • 40: Bus bar
      • 50: Support part
      • 60: Thermal image photographing unit
      • 70: Magnetic field image photographing unit
      • 80: Diagnosis part
      • H: Hole
      • W: Wire
      • DB1: Photographed thermal image data
      • DB2: Photographed magnetic field image data
      • P1: Photographed thermal image
      • P2: Photographed magnetic field image

Claims (10)

1. A battery pack diagnosis method comprising:
a battery pack manufacturing process of manufacturing a battery pack by bonding-connecting a battery cell and a wire;
a battery cell charging and discharging process of charging and discharging the battery cell through the wire;
a battery pack thermal image photographing process of photographing a thermal image of the battery pack;
a thermal image reading process of reading a bonding state of a bonded portion of the battery cell and the wire from photographed thermal image data of the thermal image;
a battery pack magnetic field image photographing process of photographing a magnetic field image of the battery pack;
a magnetic field image reading process of reading the bonding state of the bonded portion of the battery cell and the wire from photographed magnetic field image data of the magnetic field image; and
a wire bonding state defect determining process of finally determining the bonding state of the battery cell and the wire by combining thermal image reading result information obtained in the thermal image reading process and magnetic field image reading result information obtained in the magnetic field image reading process.
2. The battery pack diagnosis method of claim 1, wherein the battery pack thermal image photographing process generates the photographed thermal image by photographing a predetermined plane on which the wire is positioned, and
wherein the photographed thermal image has a predetermined pixel size less than at least one of a thickness of the wire and a size of a bonded portion of the wire.
3. The battery pack diagnosis method of claim 1, wherein the thermal image reading process comprises:
a thermal image contour generating process of extracting a predetermined contour in the photographed thermal image and generating a shape of the bonded portion of the battery cell and the wire;
a bonded portion temperature reading process of reading a temperature of the bonded portion of the battery cell and the wire from the photographed thermal image data as one of a high temperature and a low temperature;
a bonded portion abnormal connection determining process of determining the bonding state of the bonded portion of the battery cell and the wire as an abnormal connection-confirmed state when the bonded portion of the battery cell and the wire has a temperature greater than a predetermined reference temperature;
a bonded portion normal connection-considered determining process of determining the bonding state of the bonded portion of the battery cell and the wire as a normal connection-considered state when the bonded portion of the battery cell and the wire has a temperature less than the reference temperature; and
a thermal image reading result information generating process of generating the thermal image reading result information by matching position information of the bonded portion of the battery cell and the wire with the bonding state of the bonded portion of the battery cell and the wire.
4. The battery pack diagnosis method of claim 2, wherein the battery pack magnetic field image photographing process generates the magnetic field image by photographing the same predetermined plane as that photographed to obtain the photographed thermal image, and
wherein the photographed magnetic field image has a predetermined pixel size determined in correspondence to that of the photographed thermal image.
5. The battery pack diagnosis method of claim 3, wherein the magnetic field image reading process comprises:
a magnetic field image contour generating process of generating a shape of the bonded portion of the battery cell and the wire in the photographed magnetic field image by using the contour extracted from the thermal image reading process;
a bonded portion magnetic field intensity reading process of reading a magnetic field intensity of the bonded portion of the battery cell and the wire from the photographed magnetic field image data;
a bonded portion normal connection determining process of determining the bonding state of the bonded portion of the battery cell and the wire as a normal connection-confirmed state when the bonded portion of the battery cell and the wire has the magnetic field intensity greater than a predetermined reference intensity;
a bonded portion abnormal connection-considered determining process of determining the bonding state of the bonded portion of the battery cell and the wire as an abnormal connection-considered state when the bonded portion of the battery cell and the wire has the magnetic field intensity less than the reference intensity; and
a magnetic field image reading result information generating process of generating magnetic field image reading result information by matching position information of the bonded portion of the battery cell and the wire with the bonding state of the bonded portion of the battery cell and the wire.
6. The battery pack diagnosis method of claim 5, wherein the wire bonding state defect determining process finally determines the bonding state of the bonded portion of the battery cell and the wire as one state selected from a normal connection state, an abnormal connection state, and an abnormal broken state by comparing the thermal image reading result information with the magnetic field image reading result information.
7. The battery pack diagnosis method of claim 6, wherein the wire bonding state defect determining process, by comparing the thermal image reading result information with the magnetic image reading result information, finally determines:
the bonding state of the bonded portion of the battery cell and the wire as the abnormal connection state when the bonding state of the bonded portion of the battery cell and the wire is an abnormal connection-confirmed state;
the bonding state of the bonded portion of the battery cell and the wire as the normal connection state when the bonding state of the bonded portion of the battery cell and the wire is a normal connection-confirmed state; and
the bonding state of the bonded portion of the battery cell and the wire as the abnormal broken state when the bonding state of the bonded portion of the battery cell and the wire is a normal connection-considered state or an abnormal connection-considered state.
8. The battery pack diagnosis method of claim 1, wherein while the battery cell charging and discharging process is performed, the battery pack thermal image photographing process and the battery pack magnetic field image photographing process are simultaneously performed.
9. The battery pack diagnosis method of claim 1, wherein while the battery cell charging and discharging process is performed, the battery pack thermal image photographing process and the battery pack magnetic field image photographing process are performed in a predetermined order with a predetermined time difference.
10. A battery pack upon which the battery pack diagnosis method of claim 1 is performed, the battery pack comprising:
the battery cell; and
the wire connected to the battery cell.
US18/030,650 2020-11-23 2021-11-19 Method for diagnosing battery pack Pending US20230408594A1 (en)

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